From which germ layers do the following organs originate.
(a) Mesoderm: The mesoderm is the middle layer. In the embryo, it differentiates to give rise to a number of tissues and structures including bone, muscle, connective tissue, and the middle layer of the skin. (b) Endoderm is the innermost of the three primary germ layers in the very early embryo. The endoderm consists at first of flattened cells, which subsequently become columnar.
